Anatomy and vasculature of the floral nectaries of Brassica napus (Brassicaceae)

Abstract

The floral nectaries of Brassica napus L. (Argentine or Swede rape) consist of two pairs of glands which are supplied by phloem only. The lateral pair has an extensive phloem supply and produces most of the flowers' nectar, whereas the median pair is supplied by limited phloem and produces relatively little nectar. Because both lateral and median nectaries contain cells exhibiting similar structural features, the disparity in phloem supply between them could account for the observed difference in nectar production. Ultrastructural evidence suggests an energy-requiring, eccrine mechanism of nectar secretion in Brassica napus. Both apoplastic and symplastic routes for nectar movement and escape appear feasible. Stomata on the nectary surfaces may serve as exits.

Floral nectar secretion and ploidy in Brassica rapa and B napus (Brassicaceae). I. Nectary size and nectar carbohydrate production and composition

“…Except for the haploid lines, all plants were derived from seed of the 'rapid-cycling' forms of Brassica (Williams and Hill, 1986) as g/ml from g/g using the formula for conversion of refractometer readings (Bolten et al, 1979;Bbrquez and Corbet, 1991 (Davis and Gunning, 1992 (Paatela, 1962;Valle et al, 1962;Skirde, 1963;Bond, 1968), and the solute concentration of nectar for diploids is similar (Skirde, 1963) or, usually, higher (Maurizio, 1954;Paatela, 1962;Valle et al, 1962;Eriksson, 1979 (Maurizio, 1954(Maurizio, , 1956Paatela, 1962;Valle et al, 1962;Skirde, 1963;Eriksson, 1979 (Frei, 1955) and the species studied here, B napus (Frei, 1955;Davis et al, 1986) and B rapa (present results). The heavily secreting lateral nectaries are penetrated by numerous, branching sieve elements whereas the base of the larger, median nectaries lacks any vascular supply or is barely innervated by phloem.…”

Ecological aspects of the floral structure and flowering in Pulsatilla species

“…The presence of stomata in this part of the flower was reported in Lasquerella fendleri (Brassicaceae) by Kehl and Erickson [54] and at the base of the style in some Apiaceae and Asteraceae by Fahn [55] and Davis et al [56]. Kehl and Erickson [54] associate the presence of gynoecial stomata with secretion of products that can attract pollinators, which may represent an adaptation to ensure cross-pollination.…”

Mesurer la sécrétion nectarifère : exemple d'une lignée hybride F1 et de son parent mâle stérile chez le colza d'hiver (Brassica napusL.)

“…Le colza, comme l'ensemble des Brassicaceae, appartient au premier type de plante où il n'y a pas de stockage d'amidon (Davis et al, 1986(Davis et al, , 1998. Or, l'activité photosynthétique des plantes admet un optimum de température, cet optimum étant lui-même dépendant de la température à laquelle les plantes se sont développées.…”

“…Seul le nectar des deux nectaires latéraux était échantillonné dans chaque fleur (Fig. 5), ces nectaires produisant 95 % du nectar sécrété par la fleur (Davis et al, 1986(Davis et al, , 1998. Lorsque le nectar était visqueux, c'est-à-dire dans les situations de fortes concentrations et de faibles températures (Nicolson et Thornburg, 2007), situations qui intervenaient systématiquement au moins en fin d'après-midi après 16h00 GMT, les microcapillaires étaient laissés en contact avec les nectaires durant 3 à 5 minutes (Fig.…”